In my opinion the honeywell IAQ is the best thermostat you can have. First off it's a touch screen, with a 7 day program. Second this one thermostat will control all of systems components( Heat, A/c, Humidifier, Electronic Air Cleaner, etc.). Third, Honeywell makes a universal furnace control board that can connect with the IAQ modual and if your furnace fails your thermostat will display a red light from behind the plastic case and an error code on the screen which will tell your HVAC service tech what the problem is before he comes to your house, this not only saves time but also saves you the money of having your system diagnosed. But I think the most important thing is that it is easy to get installed, most homes have 3 to 5 thermostat wire already run through the wall, the IAQ only needs 3 wires from the thermostat to the modual which once again save the time and money of having new wire run through your home. Here is a link that might be useful: Coleman Heating And Air Conditioning

Normally a Ylo and O is jumpered and BK and R are Jumpered When using the Ylo terminal. A signal to Ylo creates 50% CFM from the blower, a signal to Ylo and Y the blower will run at 100% This would be used in XL19i or XL20i with 2 compressors. Say 4 ton XL20i system, has 2 compressors, a 4 ton and 2 ton compressor. In high stage blower runs at 100% with 4 ton compressor, low stage runs 2 ton compressor 50% of blower cfm capacity. BK and R with jumper removed capacity drops from High 80% and Low 40% I won't kid, it can get so mixed up with do this don't do that, that a normal install crew that only installs one of these a month may get confused and lost. This is why Trane has their communication controller XL900 with Comfort Link II and with that there is where my knowledge ends because I've spent the last 3 yrs with the Bryant Evolution and Carrier Infinity communication systems.

ibj, I feel for you, to be honest if your friend sells trane, he has got to know about the dip switches, plus he has to know about IAQ thermostats, It trane and HW IAQ for pete sake it's like bread and butter. There is nothing wrong with trane I sold/installed them for 10 yrs I know the systems very well. I also know that there are guys who sell trane that will under cut the price then leave the customer hanging and of course the customer comes here for advice when we just got through mentioning find the right install contractor. I can give the advice but you need to have your friend look this stuff up and fix it for you. You paid him, remember you didn't pay us. And I just lost a job because of a guy like your friend who undercut me and I know for a fact this long time customer of mine is in for a rude awaking because he went with a larger system and is not going to correct his zoning. But Things happen for a reason. His job loss turned into 4 other leads today. For your friend Just have him buy the IAQ stat and read the instructions it's all there and then he will know the setup for you and for the future next customer. Remember it's his job to know or to find out how and that is why you paid him. keep us up to date and if he doesn't pull through I will be glad to go through the IAQ thermostat with you.

John I am looking into the IAQ conroller as well and had issues with the documentation. I wound up going to iaqsource.com (a place where I buy HVAC supplies) and looking at the Honeywell IAQ products as well as the Honeywell smart Thermostat that is similar to the IAQ model (same programming) but does not have the separate 3 wire interface module. If you click on the product details, they have a tab for documentation. Download the install and operator manuals for both and look them over. I found the documentation for the smart thermostat to be more informative on explaining the programming, but none of them are great. I had to read them all to figure out how to hook it up and program it. I can't answer all of your questions - but the room size input is for an Energy Recovery Ventilator or it's cousin the HRV. These units cycle periodically to bring in fresh air and dump stale air from your house, while exhanging the heat (or cool) and moisture from the outgoing conditioned air to the incoming air. The IAQ contoller does this by activating the ERV/HRV and the HVAC fan (this is an option you can select). The frequency and duration of this fresh air cycle can be determined by the IAQ controller either through a square footage of the home (one optional entry) or the number of bedrooms (another optional entry). If you don't have an ERV or HRV, then you won't need to make either of these inputs. The O terminal is used to control the reversing valve on the heat pump, which it sounds like you have. The IAQ controller allows you to define if the activation of O is is associated with either A/C On or Heat On since this can vary by brand. The external temperature sensor on the IAQ contoller is used for controlling humidifiers. I currently have 2 Honeywell humidifiers on 2 of my 3 heat pumps - and each of these has their own humidifier controller connected to their own external thermometer. The humidifier contoller uses outside air temp, inside air temp, air flow, and humidity level to automatically control the humidifier water flow. If you don't have that external themometer, then you have to manually adjust the humidistat - the auto feature doesn't work unless you have that external input. It looks the the IAQ contoller has a similar feature, but the thermometer for the IAQ controller is different from the one used with the Honeywell humidifiers (it's a 1 letter difference in part number, but the tranducer tables that show conversion of outside air temperture to Ohms is quite a bit deifferent between the two). I am not sure if this thermometer input is used for anything other than display of the outside air temp and humidifier control. I had a bunch of other questions on the IAQ device since I too found the manuals lacking and I tried to send Honeywell tech support an email 2 months ago - still no response. Hopefully there will be a expert here so others can learn about how to set this device up - it looks like a great product and will make my life of managing 2 humidifiers, 1 while house dehumidifier, an ERV, and 3 heat pumps lot easier. Good luck